(1) Field of the Invention
The present invention relates to a sliding member including a sliding layer and a steel back metal, which has high corrosion resistance and high bonding strength between the sliding layer and the steel back metal.
(2) Description of Related Art
Sintered copper-based materials having a porosity of approximately 5 to 25% have been conventionally used for a sliding member for use in a fuel injection pump. The sliding member is cylindrically shaped and configured such that a fuel liquid is supplied from an outer peripheral surface side to an inner peripheral surface (sliding surface) side through pores existing in the sliding member, whereby a lubricating fluid film of the fuel liquid is formed on the inner peripheral surface (sliding surface) to support a shaft rotating at a high speed. Such sintered copper-based materials have a problem that the copper alloy is subject to corrosion due to organic acids or sulfur contained in the fuel and the fuel is contaminated by copper corrosion products. For the reason, sintered copper-based sliding materials including Ni, Al and Zn have been proposed to improve the corrosion resistance (see for example JP-A-2002-180162, JP-A-2013-217493 or JP-A-2013-237898).
Another type of sliding members have been conventionally used which are made of multi-layered sliding materials. The multi-layered sliding materials include a porous sintered layer made of a copper alloy disposed on a surface of a steel back metal via a copper plated layer, and pores and a surface of the porous sintered layer are impregnated and covered with a resin (see for example JP-A-2002-61653 or JP-A-2001-355634). It has been proposed to apply such multi-layered sliding materials to the sliding member of the fuel injection pump (see for example JP-A-2013-83304).